522 



BRAIN MECHANISMS AND LEARNING 



described by French, etc. (French, Gcrnaudt and Livingston, 1956; 

 Konigsmark, Abdullah and French, 195!^), and will not be detailed here. 

 In the present study the stimulus strength was so adjusted that the after- 

 discharges of about 60 per cent of the trials lasted 8-10 seconds. They were 

 localized to the temporal cortex, and did not spread to visual areas. 

 Following unilateral stimulation, the after-discharges appeared very rarely 

 in the contra-lateral temporal cortex (less than 5 per cent of trials). 



Four monkeys were trained on four discriminations. Fig. 8 shows the 

 learning curves. The monkeys responded at a chance level in 150 trials 

 when trained during bilateral temporal after-discharges, but learned the 

 problem during unilateral EEG discharges. The animals reached for the 

 stimulus in every trial during bi-tcmporal after-discharges. Their general 

 behaviour during this period, however, appeared to be normal. They 

 could pick up small pieces of food from among inedible objects. Some- 

 times the animals seemed to be bewildered and glanced around, but this 

 did not prevent them from reacting to the task. 



Table III 



RETENTION TEST RESULTS OBTAINED DURING EEG AFTER-DISCHARGES IN THE TEMPORAL CORTEX. 

 PERCENTAGE OF CORRECT RESPONSES IN THIRTY TRIALS. (tHE FIGURES IN ITALICS ARE BASED ON 

 FIFTEEN TRIALS.) R.G, RED I'. GREEN; T.C, TRIANGLE I'. CIRCLE; V.H, VERTICAL V. HORI- 

 ZONTAL STRIATIONS; S, SHOCK TRIALS; NS, NO SHOCK TRIALS; BILAT., BILATERAL; UNILAT., 



UNILATERAL 



The ability of the monkeys to perform the learned visual discrimina- 

 tions during either bilateral temporal or unilateral temporal after- 

 discharges was also tested. Each discrimination was tested in two days. 

 Each daily session consisted of fifteen trials with electric shocks and fifteen 

 trials without shocks presented in a balanced order. Each trial was given in 

 the same manner described before. For no-shock trials, the animal merely 

 waited for 5 seconds. The results are summarized in Table III. It is clear 

 that the animals failed to retain the learned habits under the condition of 



